§ 7-5.703. Hydrodynamic loads.

Hydrodynamic loads, the purpose of these regulations, are those induced on structures the flow of flood water moving at moderate to high velocity around the structures or parts thereof, above ground level. Such loads may occur below the ground level when openings or conduits exist which allow free flow of flood waters. Hydrodynamic loads are basically of the lateral type and relate to direct impact loads by the moving mass of water, and to drag forces as the water flows around the obstruction.

Conversion to equivalent hydrostatic loads. For the purpose of these regulations, and for cases when water velocities do not exceed ten (10) feet per second, dynamic effects of the moving water may be converted into equivalent hydrostatic loads by increasing the depth of water by an amount dh, on the upstream side and above the ground level only, equal to:

"V" is the average velocity of the water in feet per second;

"g" is the acceleration of gravity, 32.2 feet per second per second; and

"a" is the coefficient of drag or shape factor. (The value of "a", unless otherwise evaluated, shall not be less than 1.25).

The equivalent surcharge depth "dh" shall be added to the depth measured between the design level and the regulatory flood and the resultant pressures applied to, and uniformly distributed across, the vertical projected area of the building or structure which is perpendicular to the flow. Surfaces parallel to the flow or surfaces facing downstream shall be considered subject to hydrostatic pressures for depths to the regulatory flood only.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)